I really don't know. If anyone is serious about ponying up this much
money, he/she can contact me, my rough guess is between 0.5 and 1.5
years of full-time work, so you can work out the math.

I'm also not sure it's a good idea. If you want python, it would be
better to start afresh with a python version of LilyPond, and move
speed-critical things to C(++). Then, end-result will be more "pythonic"
I imagine that the end result will be slower than the current
GUILE/Scheme combo.